This application relates to scroll compressors, and in particular, to an improved idler shaft and an improved involute for use with such compressors which can reduce the expense and time involved in manufacturing the components of scroll compressors.
As is generally known, scroll compressors include a fixed scroll and an orbiting scroll, both of which contain an involute. The involutes of the fixed and orbiting scrolls intermesh, and the orbiting scroll revolves eccentrically relative to the fixed scroll, to compress air contained between the involutes of the two scrolls.
Idler shafts maintain proper orientation and alignment of the orbiting scroll relative to the fixed scroll, as well as support the thrust load of the orbiting scroll. The idler shafts also determine the orbiting radius of the orbiting scroll so that the orbiting scroll involute does not interfere with the fixed scroll involute. Because of the close tolerances which must be obtained in the operation of the scroll compressor, the idler shaft must be machined or otherwise formed to within very close tolerances.
Generally, idler shafts are made from a single piece of bar, or are cast to near net shape. They are then precision ground to maintain the critical eccentric. The grinding process is thus very expensive and very time consuming.
Similarly, the manufacture of the scroll members (i.e., the fixed and orbiting scrolls) is very expensive. Generally, the scroll members are made from a single piece of cast or bar material. The involute shape is then machined into the scroll base. To achieve a properly formed involute typically requires 6 to 8 passes. This requires specialized machining centers that are capital intensive. This makes the scroll manufacturing very expensive.